An existing connector for connecting various electronic devices, such as a computer main board and its peripheral devices or the like, comprises a receptacle connector assembled in a connection interface of a shell for an electronic device and the like, and a plug connector mating with said receptacle connector. FIG. 1 shows a receptacle connector assembled to a connection interface of a shell for an electronic device shell. The receptacle connector 10 comprises an insulating housing 101, conductive terminals arranged in the insulating housing 101 and a shielding shell 103 covering on the outside of the insulating housing 101. The receptacle connector 10 is fixedly connected to a circuit board 40, with an opening thereof for mating with a plug connector (not shown) corresponding to a connecting through-hole 201 of a connection interface 20 of an electronic device such as a computer or the like, the plug connector being electrically connected to the receptacle connector through the connecting through-hole 201.
However, with the development of the electronic devices such as a new type displayer and in order to be compatible with the existing connectors, a plug connector having an anti-incorrect-insertion mechanism has been recently developed. As shown in FIG. 2, the plug connector 30 comprises a housing 302, a mating portion 301 and a cable 303 respectively connected to both ends of the housing. A projecting block 304 for anti-incorrect-insertion is provided on the mating portion 301 for preventing incorrect insertion. The projecting block 304 of the plug connector 30 for connecting various electronic devices may vary in size. Accordingly, the connecting through-hole 201 of the connection interface 20 is provided with a corresponding fool-proof opening 202 through which the projecting block 304 of the plug connector passes, said fool-proof openings corresponding to the different projecting block 304 of the plug connector, as shown in FIGS. 3 and 4.
However, after the plug connector 30 of said structure has been inserted into the receptacle connector 10, the projecting block 304 of the mating portion 301 of the plug connector 30 will extend through the fool-proof opening 202 of the mating interface and thereby be exposed to outside the connector. Furthermore, the fool-proof opening 202 is a completely exposed opening without a plug connector 30 inserted therein. Thus, the electromagnetic signal will pass through the connection interface 20 from the fool-proof opening 202 to interfere the electronic components in the electronic devices and further to influence the anti-electromagnetic interference capability of the electronic devices.